Acrylate-based UV-curable resins are commonly used in various applications, but they often suffer from limited mechanical strength and resilience due to low free-radical polymerization. In an Advanced Materials study led by Prof. Wu Lixin from the Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, a breakthrough in 3D printing high-performance elastomers through vat photopolymerization (VPP) was achieved.
The researchers delved into the relationship between molecular weight and mechanical properties. They selected polytetramethylene ether glycols (PTMGs) with different molecular weights (Mn=1000, 2000, 3000 g mol-1) and reacted them with isophorone diisocyanate (IPDI) to create high-viscosity polyurethane blocked oligomers (PUBs).
Increasing the proportion of oligomer was identified as an effective way to boost polymerization, but it came with a viscosity challenge. The solution lay in the previously developed linear scan-based vat photopolymerization (LSVP), enabling the 3D printing of high-viscosity resin.
Through LSVP, the researchers synthesized oligomers containing tert-butyl hindered urea bonds (HUBs), which could deblock at high temperatures and re-block at room temperature. During printing, HUBs and viscous oligomers cross-linked through free radical polymerization to create green parts.
The LSVP system’s wide process window facilitated the replacement of conventional monomers with high-viscosity oligomers combined with the prepared PUBs, resulting in a 3D printable UV-curable resin.
Mechanical tests highlighted PUB2000-HMDA as the top performer, boasting the highest ultimate engineering stress at 25.9 ± 1.6 MPa and an impressive strain of 1605 ± 63%. Its tensile toughness, measured as the area beneath the strain–stress curve, reached 142.3 MJ m-3, showcasing superior mechanical properties.
Additionally, the researchers explored the impact of different chain extenders on mechanical properties. Among the tested extenders, HMDA-extended samples displayed the highest tensile strength and elongation at break.
This comprehensive study thoroughly examined the mechanical properties of high-viscosity PUB-dominated UV-curable resin under thermal treatment.
Source: Chinese Academy of Sciences